Figure 1.

NCX_Mj structure and transport mechanism. (A) Crystal structure of NCX_Mj (PDB 3V5U) in cartoon representation. Helices 1-5 (TM1-5) are light green and helices 6-10 (TM6-10) are dark green. Purple and green spheres represent the Na⁺ and Ca²⁺ ions, respectively. (B) Ion coordination, as suggested by the crystal structure of NCX_Mj. (C) 3Na⁺ ion coordination, as suggested by molecular dynamics simulations and ion-flux assays. (D) Ca²⁺ binding site. (E) Schematic representation of the ion-exchange mechanism.